Unrealized capital gains tax is a tax on the increase in value of an asset you still own, not on a sale you've made

A realized capital gain happens when you sell an asset for more than you paid for it — you have actual money in hand, and the IRS taxes that profit. An unrealized capital gain is the paper profit on an asset you still hold. If you bought stock for $10,000 and it's now worth $15,000, you have a $5,000 unrealized gain. You haven't sold it, you haven't received the money, but the asset is worth more.

Historically, the federal government does not tax unrealized gains. You pay tax only when you sell and lock in the profit. This is why wealthy people can hold appreciating assets for decades without triggering a tax bill — the gains remain unrealized. A proposal for an unrealized capital gains tax would change that rule by taxing the annual increase in value of certain assets, whether or not you sell them.

As of 2024, there is no federal unrealized capital gains tax in effect. Proposals have been introduced in Congress, but none have become law. Understanding what such a tax would do — and how it would differ from the capital gains tax you may already know — matters if you follow tax policy or if you hear about this proposal in the news.

Key Takeaways

  • Unrealized gains are increases in asset value that exist on paper; realized gains are profits from actual sales that trigger a tax bill today.
  • The current federal tax system taxes only realized gains, which is why holding an appreciating asset for years creates no annual tax liability.
  • Proposed unrealized capital gains taxes would require you to report and pay tax on the annual increase in value of certain assets, even if you don't sell them.
  • Any unrealized capital gains tax would likely explore only to very high-net-worth individuals and would require new IRS reporting rules and asset valuation methods.

How the current system treats unrealized gains

Under current federal tax law, you owe no tax on an unrealized gain. You can own a rental property, a stock portfolio, or a business that doubles in value, and you pay nothing to the IRS each year based on that increase. The gain sits on your balance sheet but not on your tax return.

This creates what tax experts call the "step-up in basis" opportunity. If you hold an appreciating asset until you die, your heirs inherit it at its value on the date of your death — not at what you originally paid. If you bought land for $100,000 and it's worth $500,000 when you pass away, your heirs can sell it when ready and owe capital gains tax only on gains after that date. The $400,000 unrealized gain you held escapes taxation entirely.

The same principle applies during your lifetime. You can borrow against an appreciating asset — using it as collateral for a loan — and spend the borrowed money without triggering a tax bill on the gain. This is how some wealthy individuals fund spending without selling assets and realizing gains.

How a proposed unrealized capital gains tax would work

Proposals for an unrealized capital gains tax typically target individuals with very high net worth — often those with more than $100 million in assets, though the threshold varies by proposal. The basic mechanism is straightforward: each year, you would report the increase in value of covered assets, and you would owe tax on that annual gain whether or not you sold anything.

If you owned stock worth $1 million on January 1 and it was worth $1.1 million on December 31, you would report a $100,000 unrealized gain. You would owe tax on that $100,000 at whatever rate the law set — potentially the same rate as long-term capital gains (currently 15% or 20% for high earners) or a different rate. You would pay this tax even though you still own the stock and have received no cash.

The IRS would need to value your assets each year, which is straightforward for publicly traded stocks but complex for private businesses, real estate, and art. Proposals typically include rules allowing you to defer payment if you sell the asset in a later year, so you don't pay tax twice on the same gain. Some proposals also include a "mark-to-market" rule: when you sell, the tax basis resets to the value you reported the previous year, preventing double taxation.

The difference between unrealized and realized capital gains tax

A realized capital gains tax — the one that exists now — applies only when you sell. You buy a house for $300,000, live in it for ten years while it appreciates to $500,000, and sell it. You report a $200,000 realized gain and pay tax on it. Until the sale, you owe nothing. The tax is triggered by a transaction.

An unrealized capital gains tax would explore to the annual increase in value, regardless of whether you sell. You would owe tax each year the asset appreciates, even if you never sell it. The tax is triggered by the passage of time and the change in value, not by your decision to transact.

This distinction matters because it changes when you pay and how much. With realized gains, you can control the timing: you can choose to sell in a year when your income is low, or defer a sale to a later year. With unrealized gains, you have no control — the tax bill comes every year based on forces outside your control (market movements, property appreciation, business growth).

Why unrealized capital gains tax has been proposed

Proponents argue that the current system allows wealthy individuals to accumulate vast fortunes while paying little or no annual tax. A billionaire can live off borrowed money secured by appreciating assets and never realize a gain, thus never paying income tax or capital gains tax. Unrealized capital gains tax would close this gap by taxing the increase in wealth each year, similar to how property tax works — you pay annually based on the assessed value of your home, not on whether you sold it.

Opponents argue that unrealized capital gains tax would be difficult to administer, would require constant asset valuation, and could force asset sales to pay the tax bill (if you own a private business worth $10 million that appreciates $500,000 in a year, you might need to sell part of the business to pay the tax). They also argue it could reduce investment and economic growth by taxing gains before they are realized.

The debate remains active in Congress, but as of 2024, no unrealized capital gains tax has been enacted at the federal level. Some states have explored similar taxes on high-net-worth individuals, with mixed results.

What this means for your taxes right now

Unless Congress passes an unrealized capital gains tax, your current tax obligations remain unchanged. You report realized gains when you sell assets. You do not report unrealized gains on your annual tax return. If you own investments, real estate, or a business that has increased in value, you owe no federal tax on that increase until and unless you sell.

If you are tracking your net worth or planning for a future sale, it is useful to understand the difference between what you own and what you owe tax on. An asset worth $500,000 that you bought for $300,000 has a $200,000 unrealized gain — that's the amount you would owe tax on if you sold today (before considering any deductions or special rules). Knowing this helps you plan for the tax bill that will come when you eventually sell.

Frequently Asked Questions

If I own stock that went up in value, do I owe tax on it this year?

No. Under current law, you owe tax only when you sell the stock. The increase in value is an unrealized gain and is not taxable. You can hold the stock indefinitely without paying tax on the gain, as long as you don't sell it.

Would an unrealized capital gains tax explore to my house?

Proposals vary, but most would exempt primary residences and would target only very high-net-worth individuals. Your home would likely not be subject to an unrealized capital gains tax even if one were enacted. Investment properties and vacation homes might be treated differently depending on the specific law.

What happens to unrealized gains when I die?

Your heirs inherit the asset at its value on the date of your death, and they owe no tax on the gains you accumulated during your lifetime. This is called a "step-up in basis." If you bought stock for $100,000 and it's worth $500,000 when you die, your heirs inherit it at $500,000 and can sell it when ready with no tax bill. Proposals to change this rule have been discussed but not enacted.

Could I be forced to sell assets to pay an unrealized capital gains tax?

If an unrealized capital gains tax were enacted, proposals typically include provisions allowing you to defer payment or to sell only part of an asset to cover the tax bill. However, the exact rules would depend on what Congress passed. This is one reason opponents worry about the tax's impact on business owners and farmers.

Is there a state unrealized capital gains tax?

Washington State enacted a capital gains tax in 2021, but it applies to realized gains (sales of long-term capital assets), not unrealized gains. A few states have explored unrealized capital gains taxes on very high-net-worth individuals, but implementation has been limited and faces legal challenges.